International Order: Defining Acts Of War

The law of war, or international humanitarian law, is a set of international rules that govern the conditions for initiating war (jus ad bellum) and the conduct of hostilities (jus in bello). The law of war defines sovereignty, nationhood, states, territories, and other critical terms. Modern laws of war address declarations of war, acceptance of surrender, the treatment of prisoners of war, military necessity, distinction, proportionality, and the prohibition of certain weapons. These laws are constantly evolving as conflicts change, and new laws can be created to address emerging issues. The lack of a central authority in international law and warfare presents challenges, as states may interpret laws to their advantage. The rules of war aim to maintain humanity in conflicts, save lives, and reduce suffering by balancing the weakening of the enemy with limiting suffering.

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Initiating war and conduct of hostilities

The laws of war, or international humanitarian law (IHL), are a set of international rules that govern the conditions for initiating war (jus ad bellum) and the conduct of hostilities (jus in bello). Jus ad bellum assumes a motive such as defending oneself from a threat or danger and presupposes a declaration of war that warns the adversary. Jus in bello involves behaving as soldiers invested with a mission for which not all violence is allowed. War begins with a declaration of war and ends with a treaty of peace or surrender agreement.

The laws of war define sovereignty and nationhood, states and territories, occupation, and other critical terms. Modern laws of war address declarations of war, acceptance of surrender, and the treatment of prisoners of war. They also cover military necessity, which is governed by several constraints: an attack or action must be intended to help defeat the enemy, it must be an attack on a legitimate military objective, and the harm caused to protected civilians or civilian property must be proportional and not excessive in relation to the anticipated military advantage.

The principle of distinction, under international humanitarian law, governs the legal use of force in an armed conflict, requiring belligerents to distinguish between combatants and protected civilians. Proportionality, another principle under international humanitarian law, dictates that belligerents must ensure that the harm caused to protected civilians or civilian property is not excessive in relation to the expected military advantage from attacking a legitimate military objective.

Modern laws of war, such as the 1949 Geneva Conventions, prohibit attacking doctors, ambulances, or hospital ships displaying a Red Cross, Red Crescent, Magen David Adom, Red Crystal, or other emblems related to the International Red Cross and Red Crescent Movement. These laws also prohibit attacking people parachuting from an aircraft in distress, regardless of the territory they are over. However, this prohibition does not apply to the dropping of airborne troops, special forces, commandos, spies, and other similar personnel, who may be attacked even if their aircraft is in distress.

Military necessity and proportionality

Proportionality is a fundamental principle of IHL that governs the protection of civilians and civilian objects in the conduct of hostilities. It has a limiting role that impacts targeting, including the choice of weapons used, the precautionary measures required, and the anticipated incidental civilian harm, which must not be disproportionate to the expected military advantage. Proportionality takes the form of both a rule and a principle, with the latter being broader in scope.

The judgement of a field commander in battle over military necessity and proportionality is rarely subject to domestic or international legal challenge unless the methods of warfare used by the commander were illegal. Military necessity also applies to weapons, particularly when a new weapon is developed and deployed. For example, the St. Petersburg Declaration of 1868 prohibited the use of projectiles under 400 grams that are either explosive or charged with combustible or inflammable substances, as they are just powerful enough to kill or wound one person, and an ordinary bullet can achieve this purpose.

Self-defence and collective self-defence

International law recognises a right to self-defence, as outlined in Chapter VII, Article 51 of the UN Charter. This is further supported by customary international law, which allows for the use of force in self-defence in situations where an armed attack has not occurred. This was established in the Caroline case, which also set a precedent for the principle of "anticipatory self-defence".

The International Court of Justice (ICJ) has specified the legal requirements for states to use armed force in self-defence in two major decisions:

• Military and Paramilitary Activities in and against Nicaragua (Nicaragua v. United States of America), 1986
• Armed Activities on the Territory of the Congo (Democratic Republic of Congo v. Uganda), 2005

In these cases, the ICJ established a close link between self-defence and aggression, contending that only an armed attack (aggression) authorises the use of armed force in individual or collective self-defence. The ICJ has also tried to clarify what level of force constitutes an armed attack, as not every act of violence will meet this threshold.

The concept of self-defence is further complicated by the question of when a state may intervene militarily in another state's territory to rescue its nationals. For example, in 1976, Israeli forces entered Uganda without permission to rescue Israeli nationals who were being held hostage by a terrorist organisation at Entebbe airport. While this raid was not condemned by the Security Council, it raises questions about the extent to which a state may intervene in another state's territory in the name of self-defence.

Collective self-defence refers to the use of collective force approved and organised by the Security Council, which is intended to substitute for unilateral uses of force by states. In the case of Nicaragua v. United States of America, the ICJ decided that there was "no rule permitting the exercise of collective self-defence in the absence of a request by the State which regards itself as the victim of an armed attack". This means that for the right of collective self-defence to apply, the attacked state must request assistance from the state(s) claiming to act in collective self-defence.

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Prohibited weapons and war crimes

The use of all weapons is restricted by the principles laid out in IHL (International Humanitarian Law), also known as the Law of Armed Conflict or the Law of War. This includes the principles of distinction and proportionality, and the prohibition of causing unnecessary suffering or superfluous injury. Some weapons are prohibited outright under international treaties, while others are restricted in the way they are used due to their expected effects in certain circumstances. The legality of a weapon depends on how it is used and who it is used against. For example, incendiary weapons designed to spread fire or burn are prohibited in all circumstances against civilians but can be used lawfully against soldiers.

Weapons that are prohibited outright under specific treaties include land mines, cluster munitions, and incendiary weapons like napalm. These weapons are governed by specific treaties or customary international law rules that restrict their use. For instance, the 1949 Geneva Conventions prohibit attacking doctors, ambulances, or hospital ships displaying a Red Cross, Red Crescent, Magen David Adom, Red Crystal, or other emblems related to the International Red Cross and Red Crescent Movement. Modern laws of war, such as Protocol I additional to the 1949 Geneva Conventions, also prohibit attacking people parachuting from an aircraft in distress, regardless of the territory they are over.

Chemical weapons are also prohibited under international law. While some chemical agents, like tear gas, may be lawful in certain circumstances (e.g., riot control), they are prohibited as a method of warfare. The use of white phosphorus, which can act as a chemical weapon, is a contentious issue. White phosphorus spontaneously ignites when it comes into contact with oxygen, producing an extremely hot flame and dense white smoke. While it can be used lawfully to create a smokescreen, its use may breach IHL principles such as proportionality and distinction if used against a target.

The Arms Trade Treaty, ratified by 113 states as of 2014, regulates the transfer, sales, and export of weapons by these states. The lack of a formal final authority on international law and warfare can complicate the interpretation and enforcement of these laws. States with advantageous interpretations may exploit this lack of authority, knowing that severe punishment is unlikely. Nevertheless, breaches of international humanitarian law can be tried in national courts or by the International Criminal Court at The Hague.

Treatment of prisoners of war

The treatment of prisoners of war is governed by international humanitarian law (IHL), which offers a wide range of protections for prisoners of war and detainees in armed conflict. The laws of war are a component of international law that regulates the conduct of hostilities (jus in bello) and defines sovereignty, nationhood, states, territories, and other critical terms.

The first traces of laws of war can be found in the Code of Hammurabi, dating back to 1750 in ancient Babylon. However, it was the events of World War I and World War II, with their widespread denial of civil rights and liberties, that had a profound effect on shaping modern international law, including prisoners' rights. The Third Geneva Convention, which came into force on October 21, 1950, significantly revised and replaced the 1929 Geneva Convention on Prisoners of War.

The Geneva Conventions and Additional Protocol II provide that people deprived of their liberty due to conflict must be treated humanely in all circumstances, regardless of the reason for their arrest and detention. They are protected against murder, torture, and cruel, humiliating, and degrading treatment. The United Nations Standard Minimum Rules for the Treatment of Prisoners, which came into force in 1955, offer guidelines in international and municipal law regarding the treatment of prisoners.

Prisoners of war have the right to humane treatment, which includes protection from violence causing death or seriously endangering health, physical mutilation, or scientific or medical experiments. They are also entitled to protection from acts of intimidation, insults, and public curiosity, as well as protection from reprisals. Prisoners must be provided with adequate food, water, shelter, and clothing, as well as sanitary living conditions and religious freedom. They have the right to exercise, adequate physical and psychological treatment, and the right to keep personal items, including money. Additionally, prisoners of war must be allowed to communicate with their representatives, the International Committee of the Red Cross, and other relevant authorities.

In terms of legal rights, no prisoner of war may be tried or sentenced for an act that is not forbidden by the law of the detaining power or international law at the time the act was committed. They cannot be coerced into admitting guilt, and they have the right to present a defence with the assistance of counsel. The death sentence cannot be pronounced on a prisoner of war unless the court has been made aware of the potential for such a sentence under the laws of the detaining power.

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